Liquid crystalline medium and liquid crystal display

ABSTRACT

The instant invention relates to liquid crystalline media comprising a dielectrically positive component, component A, consisting of dielectrically positive compounds, comprising one or more compounds of formula I and one or more compounds of formula II 
                         
wherein the parameters have the meaning given in the specification and to liquid crystal displays comprising these media, especially to active matrix displays.

FIELD OF THE INVENTION

The present invention relates to liquid crystalline media and to liquid crystal displays comprising these media, especially to displays addressed by an active matrix and in particular to displays of the TN-type.

PROBLEM TO BE SOLVED AND STATE OF THE ART

Liquid Crystal Displays (LCDs) are widely used to display information. Electro-optical modes employed are e.g. the twisted nematic (TN)-, the super twisted nematic (STN)-, the optically compensated bend (OCB)- and the electrically controlled birefringence (ECB)-mode with their various modifications, as well as others. Besides these modes, which all do use an electrical field, which is substantially perpendicular to the substrates, respectively to the liquid crystal layer, there are also electro-optical modes employing an electrical field substantially parallel to the substrates, respectively the liquid crystal layer, like e.g. the In-Plane Switching mode (as disclosed e.g. in DE 40 00 451 and EP 0 588 568). Especially this electro-optical mode is used for LCDs for modern desk-top monitors.

The liquid crystals according to the present invention are preferably used in TN-AM displays.

For these displays new liquid crystalline media with improved properties are required. Especially the birefringence (Δn) should be sufficiently high. Further, the dielectric anisotropy (Δ∈) should be high enough to allow a reasonably low operation voltage. Preferably Δ∈ should be higher than 7 and very preferably be higher than 9 or even higher than 10 but preferably not higher than 19 and in particular not higher than 15. Otherwise the resistivity of the mixtures tends to become unacceptably low for most TN-AMDs, leading to a poor voltage holding ratio. Besides this parameter, the media have to exhibit a suitably wide range of the nematic phase, a rather small rotational viscosity and, as mentioned above, an at least a moderately high specific resistivity.

The displays according to the present invention are preferably addressed by an active matrix (active matrix LCDs, short AMDs), preferably by a matrix of thin film transistors (TFTs). However, the inventive liquid crystals can also beneficiously be used in displays with other known addressing means.

There are various different display modes using composite systems of liquid crystal materials of low molecular weight together with polymeric materials such as e.g. polymer dispersed liquid crystal (PDLC)-, nematic curvilinearily aligned phase (NCAP)- and polymer network (PN)-systems, as disclosed for example in WO 91/05 029 or axially symmetric microdomain (ASM) systems and others. In contrast to these, the modes especially preferred according to the instant invention are using the liquid crystal medium as such, oriented on surfaces. These surfaces typically are pre-treated to achieve uniform alignment of the liquid crystal material The display modes according to the instant invention preferably use an electrical field substantially parallel to the composite layer.

LCDs are used for direct view displays, as well as for projection type displays.

Liquid crystal compositions with a suitable value of the birefringence for LCDs and especially for AMD displays are well known. Examples of technically advanced compositions for such applications containing compounds of the formulae

are known e.g. from WO 01/79 379. These compositions, however, do have significant drawbacks. Most of them have, amongst other deficiencies, too high values of the birefringence and especially a rotational viscosity, which is too high and lead to unfavourably long response times.

Thus, there is a significant need for liquid crystalline media with suitable properties for practical applications such as a wide nematic phase range, appropriate optical anisotropy Δn, according to the display mode used, an appropriately high Δ∈, a sufficiently high resistivity and, in particular, a low rotational viscosity.

PRESENT INVENTION

Surprisingly, it now has been found that liquid crystalline media with a suitably high Δ∈, a suitable phase range, and Δn can be realised, which do not exhibit the drawbacks of the materials of the prior art, i.e. which have a significantly lower rotational viscosity compared to media of the state of the art having the same clearing point. Thus they allow to realise displays with significantly reduced response times.

These improved liquid crystalline media according to the instant application are comprising at least the following components:

-   -   a dielectrically positive component, component A, consisting of         dielectrically positive compounds, preferably comprising one or         more compounds of formula I

wherein

-   -   R¹ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy         with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or         fluorinated alkenyl with 2 to 7 C-atoms,     -   X¹ is F, Cl or fluorinated alkyl or fluorinated alkoxy, each         with 1 to 4 C-atoms, preferably F or Cl, most preferably F and

-   -    independently of each other, are

preferably

and preferably

-   -   Z¹¹ and Z¹² are, independently of each other, —CH₂—CH₂—,         —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O—, —CH═CH—,         —CF═CF—, —CF═CH—, —CH═CF—, —C≡C— or a single bond, preferably         both are a single bond,     -   L¹¹ and L¹² are, independently of each other, H or F, preferably         L¹¹ is F and most preferably L¹¹ and L¹² both are F,     -   one or more compounds of formula II

wherein

-   -   R² is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy         with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or         fluorinated alkenyl with 2 to 7 C-atoms, preferably alkyl or         alkenyl,

-   -    preferably

-   -   Z² is —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—,         —CO—O— or a single bond, preferably a single bond and     -   X² is F, Cl or fluorinated alkyl or fluorinated alkoxy each with         1 to 4 C-atoms, preferably F, OCF₃ or CF₃,     -   optionally one or more compounds, preferably selected from the         group of compounds of formulae of formula III and IV

wherein

-   -   R³ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy         with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or         fluorinated alkenyl with 2 to 7 C-atoms, preferably alkyl or         alkenyl,

preferably

most preferably

-   -   Z³¹ and Z³² are, independently of each other, —CH₂—CH₂—,         —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O— or a         single bond, preferably one of Z³¹ and Z³² is —CO—O— and the         other is a single bond, most preferably Z³¹ is —CO—O— and Z³² is         a single bond,     -   L³¹ and L³² are, independently of each other, H or F, preferably         L³¹ is H and most preferably L³¹ and L³² both are H,

wherein

-   -   R⁴ is alkyl alkoxy, fluorinated alkyl or fluorinated alkoxy with         1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or         fluorinated alkenyl with 2 to 7 C-atoms,

most preferably

preferably

most preferably

-   -   Z⁴¹ and Z⁴² are, independently of each other, —CH₂—CH₂—,         —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O— or a         single bond, preferably —CO—O— or a single bond,     -   L⁴¹ and L⁴² are, independently of each other, H or F, preferably         L⁴¹ is F and most preferably L⁴¹ and L⁴² both are F,     -   and optionally further dielectrically positive compounds,         -   optionally, preferably obligatorily, a dielectrically             neutral component, component B, consisting of dielectrically             positive compounds, preferably comprising one or more             compounds of formula V

wherein

-   -   R⁵¹ and R⁵², independently of each other, are alkyl, alkoxy,         fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or         alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2         to 7 C-atoms, preferably alkyl or alkenyl,     -   Z⁵ is —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—,         —CO—O—, —CH═CH—, CF═CF—, —CF═CH—, —CH═CF— or a single bond,         preferably —CF₂—O— or —CH₂—O—, most preferably —CF₂—O—, and     -   n is 0 or 1, and         -   optionally a dielectrically negative component, component C,             consisting of dielectrically negative compounds.

Preferred are liquid crystal compositions comprising in component A one or more compounds selected from the group of formulae I-1 to I-5

wherein

-   -   R¹, L¹¹ and L¹² have the respective meanings given under formula         I above and     -   L¹³, independently of the other parameters, has the meaning         given for L¹¹ under formula I above, preferably     -   R¹ is n-alkyl with 1 to 7, preferably with 1 to 5 C-atoms,     -   L¹¹, L¹² and L¹³ are, independently of each other, H or F,         generally preferably at least one of L¹¹ to L¹³ is F, most         preferably at least one of L¹¹ and L¹³, most preferably at least         two of L¹¹ to L¹³ are F.

Especially preferred are liquid crystal compositions comprising compounds of formula I-1 wherein L¹¹, L¹² and L¹³ are all F and/or compounds of formula I-2-wherein L¹¹ and L¹² are, independently of each other, H or F and L¹³ is F and/or compounds of formula I-3 wherein L¹¹ and L¹² are H or F, preferably H and L¹³ is F and/or compounds of formula I-4 and/or formula I-5 wherein L¹¹ and L¹² are F and preferably L¹³ is F.

Especially preferred the compounds of formulae I-1 to I-3 are selected from the respective groups I-1a to I-1d, I-2a to I-2e, I-3a to I-3f, I4a to I4d and I5a to I5d

wherein

-   -   R¹ has the meaning given under formulae I-1 to I-5 above.

Especially preferred are formulations comprising one or more compounds of formula I-1d and/or one or more compounds of formula I-2b and/or one or more compounds of formula I-3d and/or one or more compounds of formulae I-4d and/or I-5b.

Preferred are liquid crystal compositions comprising in component A one or more compounds selected from the group of formulae II-1 and II-2

wherein

-   -   R², X² and

have the respective meanings given under formula IV above and preferably

-   -   R² is n-alkyl with 1 to 5 C-atoms,     -   X² is F or OCF₃ and

Especially preferred the compounds of formulae II-1 and II-2 are selected from the respective groups II-1a to II-1d and II-2a and II-2b

wherein

-   -   R² has the meaning given under formulae II-1 and II-2 above.

Preferably component A of the compositions according to the present invention comprise one or more compounds of formula II-1a and/or one or more compounds of formula II-1d, most preferably one or more compounds of formula II-1d.

Preferred are liquid crystal compositions comprising in component A one or more compounds selected from the group of formulae III-1 and III-2

wherein

-   -   R³, L³¹, L³² and

have the respective meanings given under formula III above and preferably

-   -   R³ is n-alkyl with 1 to 7, preferably 1 to 5 C-atoms, or         1E-alkenyl with 2 to 7, preferably 2 or 3 C-atoms,

preferably

-   -   L³¹ and L³² both are H.

Especially preferred the compounds of formulae III-1 and III-2 are selected from the respective groups III-1a to III-1h and III-2a to III-2c

wherein

-   -   R³ has the meaning given under formulae III-1 and III-2 above         and preferably is alkyl.

Especially preferred are liquid crystal formulations comprising one or more compounds selected from the group of compounds of formulae III-1b, III-2a and III-2b and in particular such formulations comprising one or more compounds of each of these formulae.

Preferred are liquid crystal compositions comprising in component A one or more compounds selected from the group of formulae IV-1 to IV-9

wherein

-   -   R⁴, L⁴¹ and L⁴² have the respective meanings given under formula         IV above and     -   L⁴³, independently of the other parameters, has the meaning         given for L⁴¹ under formula IV above, preferably     -   R⁴ is n-alkyl with 1 to 7 C-atoms, or 1E-alkenyl alkenyl with 2         to 7 C-atoms,     -   L⁴¹, L⁴² and L⁴³ are, independently of each other, H or F,         preferably at least one of L⁴¹ to L⁴³ is F, most preferably at         least one of L⁴¹ and L⁴³, most preferably at least two of L⁴¹ to         L⁴³ are F.

Especially preferred the compounds of formulae IV-1 to IV-8 are selected from the respective groups IV-1 a to IV-1c, IV-2a and IV-2b, IV-3a to IV-3d, IV-a and IV-b, IV5-a to IV-5c, IV-6a to IV-6f, IV7a and IV7-b, IV8-a and IV8-b

-   -   R⁴ has the meaning given under formulae IV-1 to IV-8 above and         preferably is alkyl or alkenyl.

Preferably component A comprises one or more compounds selected from the group of compounds of formulae IV-1b, IV-1c, IV-2b, IV3-b, IV4-a, IV-3c, IV-4d, IV-5c, IV-6c, IV-6f, IV-7b and IV-8b, most preferably selected from the group of formulae IV-1c, IV-2b, IV-4d, IV-5c and IV-6c.

Preferably the liquid crystal mixtures according to the present invention comprise a dielectrically neutral component, component B. This component has a dielectric anisotropy in the range from −1.5 to +3. Preferably it consists essentially and especially preferably entirely of dielectrically neutral compounds. Preferably this component comprises one ore more dielectrically neutral compounds selected from the group of formulae V-1 to V-3

wherein

-   -   R⁵¹ and R⁵² have the meaning given under formula V above and in         formula V-1 preferably at least one of R⁵¹ and R⁵² is alkenyl,         preferably vinyl or 1E-alkenyl, in formula V-2 preferably R⁵¹ is         alkenyl, preferably vinyl or 1E-alkenyl with 3 or more C-atoms         and R⁵² preferably is alkyl, preferably n-alkyl, preferably         methyl or ethyl and in formula V-3 preferably both R⁵¹ and R⁵²         are, independently of each other, alkyl, preferably n-alkyl.

Further preferred are liquid crystalline media in which the dielectrically positive component, component A comprises one or more compounds of formula VI

wherein

-   -   R⁶ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy         with 1 to 7 C-atoms, alkenyl, alkenyloxy, alkoxyalkyl or         fluorinated alkenyl with 2 to 7 C-atoms,     -   X⁶ is F, Cl or fluorinated alkyl or fluorinated alkoxy, each         with 1 to 4 C-atoms, preferably F or Cl, most preferably F and     -   m is 0 or 2.     -   wherein, optionally, two of the 6-membered rings may be linked         by a group selected from         -   —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—,             —CH═CH—, —CF═CF—, —CF═CH—, —CH═CF—, —C≡C——O—, preferably             —CH₂—CH₂— and —CF₂—O—, most preferably —CH₂—CH₂—     -   and from which compounds of formula II are excluded.

In a preferred embodiment the liquid crystal composition comprises component B which one or more compounds of formula VII

wherein

-   -   R⁷¹ and R⁷², independently of each other, have the meaning given         for R¹ under formula I above,

-   -    independently of each other, and in case

-   -    is present twice, also these, independently of each other, are

-   -    preferably at least one of

-   -    and preferably at least one of

-   -   Z⁷¹ and Z⁷² are, independently of each other, and in case Z⁷¹ is         present twice, also these independently of each other, —CH₂CH₂—,         —COO—, trans —CH═CH—, trans —CF═CF—, —CH₂O—, —CF₂O— or a single         bond, preferably at least one of them is a single bond and most         preferably all are a single bond and     -   k is 0, 1 or 2, preferably 1 or 2     -   from which compounds of formula V are excluded.

Optionally the liquid crystal mixtures according to the present invention comprise a dielectrically negative, component C. This component has a dielectric anisotropy of −1.5 or less, and consists of dielectrically negative compounds having a dielectric anisotropy of −1.5 or less. This component C preferably comprises of compounds formula VIII

wherein

-   -   R⁸¹ and R⁸² independently of each other have the meaning given         for R¹ under formula I above,

-   -    Preferably

-   -   Z⁸¹ and Z⁸² are, independently of each other, —CH₂CH₂—, —COO—,         trans —CH═CH—, trans —CF═CF—, —CH₂O—, —CF₂O—, —CH₂—O—, —O—CH₂—,         —CH═CH—, —CF═CF—, —CF═CH—, —CH═CF—, —C≡C— or a single bond,         preferably at least one of them is a single bond and most         preferably both are a single bond,     -   L⁸¹ and L⁸² are, independently of each other, ═C(—F)— or ═N—,         preferably at least one of them is ═C(—F)— and most preferably         both of them are ═C(—F)— and     -   i is 0 or 1.

Further preferred are liquid crystalline media in which the dielectrically positive component, component A comprises one or more compounds of formula IX

wherein

-   -   R⁹ and X⁹ have the respective meanings given for R⁶ and X⁶ under         formula VI above and preferably     -   R⁹ is n-alkyl with 1 to 5 C-atoms and     -   X⁹ is F, Cl, —CF₃ or —OCF₃, most preferably F.

The compounds of formula VI are preferably selected from the group of sub-formulae VI-1 to VI-18

wherein

-   -   R⁶ and X⁶ have the respective meanings given under formula VI         above and preferably     -   R⁶ is n-alkyl with 1 to 5 C-atoms or alkenyl with 2 to 5 C-atoms         and     -   X⁶ is F, Cl, —CF₃ or —OCF₃, preferably F or Cl and most         preferably F.

Preferably the medium contains compounds of formula VI selected from the group of sub-formulae VI-7 to VI-15 and in particular VI-8 and VI-9.

The compounds of formula VII are preferably selected from the group of sub-formulae VII-1 to VII-10

wherein

-   -   R⁷¹ and R⁷² have the meaning given under Formula VII above.

Most preferably the medium contains compounds of formula VII selected from the group of sub-formulae VII-1, VII-2, VII-4, VII-6, VII-8 and VII-10 and in particular VII-4, VII-6, VII-8 and VII-10.

Especially preferred are the media comprising compounds of formula IX selected from the group of sub-formulae IX-1 to IX-4

wherein

-   -   R⁹ and X⁹ have the respective meanings given under formula IX         above.

Preferably the dielectrically positive component, component A comprises one or more compounds each of formulae I, II, III and IV and the dielectrically neutral component B comprises one or more compounds of formula V.

Preferably the dielectrically positive component, component A predominantly and preferably entirely consists of the compounds mentioned, i.e. of the compounds of formulae I, II, III, IV, VI and IX, preferably of the compounds of formulae I, II, III, and IV, the dielectrically neutral component B predominantly and preferably entirely consists of formulae V and VII, preferably of formula V and the dielectrically negative component C predominantly and preferably entirely consists of compounds formula VIII.

In a preferred embodiment the liquid crystal composition consists predominantly, preferably entirely of components A and B, preferably of component A.

The concentration of component A in the formulations according to the instant invention is preferably in the range from 50% to 100%, preferably in the range from 60% to 97%, whereas in a first preferred embodiment the concentration of component A in the formulations is in the range from 50% to 75%, preferably in the range from 55% to 75%, in a second preferred embodiment the concentration of component A in the formulations is in the range from 80% to 100%, preferably in the range from 90% to 98%.

The concentration of component B in the formulations according to the instant invention is preferably in the range from 0% to 50%, preferably in the range from 3% to 45%, whereas in the first preferred embodiment referred to above, the concentration of component B in the formulations is in the range from 20% to 50%, preferably in the range from 25% to 45% and in particular in the range from 30% to 40%, in the second preferred embodiment referred to above, the concentration of component B in the formulations is in the range from 0% to 20%, preferably in the range from 2% to 16% and in particular in the range from 6% to 19%

The concentration of compounds of formula I in the formulations according to the instant invention is preferably in the range from 3% to 30%, preferably in the range from 5% to 20% and in particular in the range from 6% to 19%

The concentration of compounds of formula II in the formulations according to the instant invention is preferably in the range from 1% to 25%, preferably in the range from 2% to 20% and in particular in the range from 3% to 15%.

The concentration of compounds of formula III in the formulations according to the instant invention is preferably 10% or more, preferably. 15% or more, more preferably 20% or more and most preferably 25% or more. It is preferably in the range from 13% to 45%, more preferably in the range from 15% to 40% and most preferably in the range from 20% to 35%.

The concentration of compounds of formula IV in the formulations according to the instant invention is preferably in the range from 15% to 60%, more preferably in the range from 20% to 55% and most preferably in the range from 25% to 50%.

The concentration of compounds of formula V in the formulations according to the instant invention. is preferably in the range from 0% to 50%, more preferably in the range from 2% to 45% and most preferably in the range from 4% to 40%. Depending on the desired polarity of the formulation the upper limit of the concentration of compounds of formula V may also be less, preferably 20% or less, more preferably 15 or less and most preferably 10% or less.

The concentration of the single compounds should be chosen to be not too large. Typical upper limits are in the range of 5 to 20% per individual homologue. The allowable upper limit of the concentration depends on the type of the compound and on the envisaged application, especially the requirement for the lower temperature limits for operation and storage. Generally, the upper limit of the concentration it is lower for compounds with four rings than for compounds with three rings and for these lower than for compounds with two rings. Also generally the upper allowable limit of the concentration is lower for more polar compounds, i.e. for dielectrically neural and for dielectrically positive compounds the limit is lower for compounds with a larger dielectric anisotropy compared to compounds with a smaller dielectric anisotropy. Within a series of homologous compounds the limit typically decreases with increasing length of the side chain, Obviously there are deviations from these rules.

For some of the compounds, which are preferably present in the liquid crystal formulations according to the present invention, preferred upper limits of the concentration of the individual homologues have been determined.

The concentration of compounds of formula I-1d with R² being an alkyl group is preferably 11% or less per homologous compound.

The concentration of compounds of formula II-1d with R² being an alkyl group, preferably a propyl group, is preferably 10% or less and especially preferred 8% or less per homologous compound.

The concentration of compounds of formula III-1b with R¹ being an ethyl group is preferably 11% or less, whereas the concentration of compounds of formula III-1b with R¹ being an n-propyl group is preferably 9% or less.

The concentration of compounds of formula V-3 with R⁵¹ and R⁵², independently of each other, being an alkyl group is preferably 8% or less and especially preferred 5% or less per homologous compound.

Preferably the liquid crystalline media according to the instant invention contain a component A comprising, preferably predominantly consisting of and most preferably entirely consisting of compounds selected from the group of formulae I to IV.

Comprising in this application means in the context of compositions that the entity referred to, e.g. the medium (the formulation) or the component, contains the component or components or of the compound or compounds in question, preferably in a total concentration of 10% or more and most preferably of 20% or more, unless explicitly stated otherwise.

Predominantly consisting, in this context, means that the entity referred to contains 80% or more, preferably 90% or more and most preferably 95% or more of the component or components or of the compound or compounds in question unless explicitly stated otherwise.

Entirely consisting, in this context, means that the entity referred to contains 98% or more, preferably 99% or more and most preferably 100.0% of the component or components or of the compound or compounds in question unless explicitly stated otherwise.

Preferably component A comprises one or more compounds of formula I, preferably compounds in wherein X¹ is F, preferably of formula I-1 and in particular of formula I-1d.

Preferably component A further comprises one or more compounds of formula II, wherein the ring A² is trans-1,4-cyclohexylene and preferably X² is CF₃, most preferably of formula II-1 and in particular of formula II-1d.

Preferably component A also comprises one or more compounds of formula III, preferably compounds wherein Z³¹ is —CO—O— and/or Z³² is a single bond and/or L³¹ is F, preferably one or more compounds of formula III-1 and/or one or more compounds of formula III-2, especially preferred one or more compounds of formula III-1e and/or one or more compounds of formula III-2a and/or one or more compounds of formula III-2b.

Also preferably, component A comprises one or more compounds of formula IV, preferably compounds wherein L⁴¹ is F and/or Z⁴¹ is a single bond or a —CO—O— and/or Z⁴² is a single bond, preferably one or more compounds of formula IV-1 and/or one or more compounds of formula IV-2, and/or one or more compounds of formula IV-3, especially preferred one or more compounds of formula IV-1b and/or one or more compounds of formula IV-1c and/or one or more compounds of formula IV-2b and/or one or more compounds of formula IV-4b.

Preferably, component B comprises one or more compounds of formula V, preferably compounds wherein R⁵¹ and R⁵² are independently of each other alkyl or alkenyl, preferably n-alkyl including methyl and ethyl or 1E-alkenyl including vinyl, preferably one or more compounds of formula V-1 and/or one or more compounds of formula V-2, and/or one or more compounds of formula V-3, especially preferred one or more compounds of formula V-1 wherein R⁵¹ and R⁵² are, independently of each other, alkyl and/or one or more compounds of formula V-1 wherein R⁵¹ is alkyl and R⁵² is alkenyl and/or one or more compounds of formula V-2 wherein R⁵¹ is alkenyl and R⁵² is alkyl and/or one or more compounds of formula V-3 wherein R⁵¹ and R⁵² are, independently of each other, alkyl.

In a preferred embodiment the liquid crystalline media according to the instant invention contains a component B predominantly consisting of and most preferably entirely consisting of compounds of formula V.

Especially preferred are media comprising compounds selected from the group of formulae VI-8, VI-11 and VI-13 and/or VI-9, VI-12 and VI-15, in particular with R⁶ being alkenyl, especially vinyl.

In a further preferred embodiment the liquid crystal medium contains a liquid crystal component C, which is preferably predominantly consisting of and most preferably entirely consisting of compounds of formula VIII.

This component C may be present, and preferably is present, besides components A and B.

Also other mesogenic, as well as non-mesogenic, compounds, which are not explicitly mentioned above, can optionally and beneficiously be used in the media according to the instant invention. Such compounds are known to the expert in the field.

Optionally, the inventive media can comprise further liquid crystal compounds in order to adjust the physical properties. Such compounds are known to the expert. Their concentration in the media according to the instant invention is preferably 0% to 30%, more preferably 0% to 20% and most preferably 0.5% to 15%.

Preferably the liquid crystal medium contains 50% to 100%, more preferably 70% to 100% and most preferably 80% to 100% and in particular 90% to 100% totally of components A, B and C, which contain, preferably predominantly consist of and most preferably entirely consist of one or more of compounds of formulae I to and VIII, respectively.

The liquid crystal media according to the instant invention are characterized by a clearing point of 66° C. or more, preferably of 70° C. or more and in particular of 75° C. or more. Obviously also significantly higher clearing points can be beneficiously realised.

The Δn of the liquid crystal media according to the instant invention is preferably in the range from 0.07 to 0.12, preferably in the range of 0.075 to 0.115, more preferably in the range of 0.075 to 0.110, most preferably in the range of 0.080 to 0.105 and in particular in the range of 0.080 to 0.100.

The Δ∈, at 1 kHz and 20° C., of the liquid crystal media according to the invention is 6.0 or more, preferably 9.0 or more, most preferably 10.0 or more and in particular 11.0 or more. It is, however, preferably 17.0 or less, more preferably 15.0 or less and most preferably 12.0 or less.

Preferably the threshold voltage of the liquid crystal media according to the invention are in the range from 0.8 V to 1.8 V, more preferably in range from 0.9 V to 1.7 V, more preferably in range from 0.9 V to 1.6 V, and in particular in the range from 1.0 V to 1.3 V or in the range from 1.5 V to 1.6 V, depending on the driver used for the display.

The operating voltages of the liquid crystal media according to the invention are preferably those of 2.5 V-, 3.3 V-, 4 V- or 5 V-drivers. Particularly preferred are those of 4 V- and 5 V-drivers.

The rotational viscosity of the liquid crystal media according to the invention are preferably in the range from 50 mPa·s to 200 mPa·s, preferably in the range from 60 mPa·s to 180 mPa·s and in particular in the range from 70 mPa·s to 140 mPa·s.

For media with a threshold voltage in the range from 1.0 V to 1.3 V the rotational viscosity is preferably in the range from 120 mPa·s to, 180 mPa·s , whereas for media with a threshold voltage in the range from 1.5V to 1.6V the rotational viscosity is preferably in the range from 70 mPa·s to 130 mPa·s .

Preferably the nematic phase of the inventive media extends at least from 0° C. to 65° C., more preferably at least from −20° C. to 70° C., most preferably at least from −30° C. to 80° C. and in particular at least from −40° C. to 80° C., wherein at least means that preferably the lower limit is under cut, wherein the upper limit is surpassed.

In the present application the term dielectrically positive compounds describes compounds with Δ∈>3.0, dielectrically neutral compounds are compounds with −1.5≦Δ∈≦3.0 and dielectrically negative compounds are compounds with Δ∈<−1.5. The same definition is used for components. Δ∈ is determined at 1 kHz and 20° C. The dielectric anisotropies of the compounds is determined from the results of a solution of 10% of the individual compounds in a nematic host mixture. The capacities of these test mixtures are determined both in a cell with homeotropic and with homogeneous alignment. The cell gap of both types of cells is approximately 20 μm. The voltage applied is a rectangular wave with a frequency of 1 kHz and a root mean square value typically of 0.5 V to 1.0 V, however, it is always selected to be below the capacitive threshold of the respective test mixture.

For dielectrically positive compounds the mixture ZLI-4792 and for dielectrically neutral, as well as for dielectrically negative compounds, the mixture ZLI-3086, both of Merck KGaA, Germany are used as host mixture, respectively. The dielectric permittivities of the compounds are determined from the change of the respective values of the host mixture upon addition of the compounds of interest and are extrapolated to a concentration of the compounds of interest of 100%. Components having a nematic phase at the measurement temperature of 20° C. are measured as such, all others are treated like compounds.

The term threshold voltage refers in the instant application to the optical threshold and is given for 10% relative contrast (V₁₀) and the term saturation voltage refers to the optical saturation and is given for 90% relative contrast (V₉₀) both, if not explicitly stated otherwise. The capacitive threshold voltage (V₀, also called Freedericksz-threshold V_(Fr)) is only used if explicitly mentioned.

The ranges of parameters given in this application are all including the limiting values, unless explicitly stated otherwise.

Throughout this application, unless explicitly stated otherwise, all concentrations are given in mass percent and relate to the respective complete mixture, all temperatures, e.g. the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T (N,I) of the liquid crystals are given in degrees centigrade (Celsius) and all differences of temperatures in degrees centigrade, unless explicitly stated otherwise. All physical properties have been and are determined according to “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status November 1997, Merck KGaA, Germany and are given for a temperature of 20° C., unless explicitly stated otherwise. The optical anisotropy (Δn) is determined at a wavelength of 589.3 nm. The dielectric anisotropy (Δ∈) is determined at a frequency of 1 kHz. The threshold voltages, as well as all other electro-optical properties have been determined with test cells prepared at Merck KGaA, Germany. The test cells for the determination of Δ∈ had a cell gap of 22 μm. The electrode was a circular ITO electrode with an area of 1.13 cm² and a guard ring. The orientation layers were lecithin for homeotropic orientation (∈∥) and polyimide AL-1054 from Japan Synthetic Rubber for homogeneuous orientation (∈_(⊥)). The capacities were determined with a frequency response analyser Solatron 1260 using a rectangular wave with a voltage of 0.3 V_(rms). The light used for the electro-optical measurements was white light. The set up used was a commercially available equipment of Otsuka, Japan. The characteristic voltages have been determined under perpendicular observation. The threshold-(V₁₀) mid grey-(V₅₀)- and saturation voltages (V₉₀) have been determined for 10%, 50% and 90% relative contrast, respectively under perpendicular observation.

The liquid crystal media according to the present invention can contain further additives and chiral dopants in usual concentrations. The total concentration of these further constituents is in the range of 0% to 10%, preferably 0.1% to 6%, based on the total mixture. The concentrations of the individual compounds used each are preferably in the range of 0.1% to 3%. The concentration of these and of similar additives is not taken into consideration for the values and ranges of the concentrations of the liquid crystal components and compounds of the liquid crystal media in this application.

The inventive liquid crystal media according to the present invention consist of several compounds, preferably of 3 to 30, more preferably of 8 to 20 and most preferably of 10 to 18 compounds.

These compounds are mixed in conventional way. As a rule, the required amount of the compound used in the smaller amount is dissolved in the compound used in the greater amount. In case the temperature is above the clearing point of the compound used in the higher concentration, it is particularly easy to observe completion of the process of dissolution. It is, however, also possible to prepare the media by other conventional ways, e.g. using so called pre-mixtures, which can be e.g. homologous or eutectic mixtures of compounds or using so called multi-bottle-systems, the constituents of which are ready to use mixtures themselves.

By addition of suitable additives, the liquid crystal media according to the instant invention can be modified in such a way, that they are usable in all known types of liquid crystal displays, either using the liquid crystal media as such, like TN-, TN-AM-, IPS- and OCB-LCDs and in particular in TN-AMDs.

In the present application and especially in the following examples, the structures of the liquid crystal compounds are represented by abbreviations also called acronyms. The transformation of the abbreviations into the corresponding structures is straight forward according to the following two tables A and B. All groups C_(n)H_(2n+1) and C_(m)H_(2m+1) are straight chain alkyl groups with n respectively m C-atoms. The interpretation of table B is self-evident. Table A lists the abbreviations for the cores of the structures only. The individual compounds are denoted by the abbreviation of the core, followed by a hyphen and a code specifying the substituents R¹, R², L¹ and L² as follows:

Code for R¹, R², L¹, L² R¹ R² L¹ L² nm C_(n)H_(2n+1) C_(m)H_(2m+1) H H nOm C_(n)H_(2n+1) OC_(m)H_(2m+1) H H nO.m OC_(n)H_(2n+1) C_(m)H_(2m+1) H H n C_(n)H_(2n+1) CN H H nN.F C_(n)H_(2n+1) CN F H nN.F.F C_(n)H_(2n+1) CN F F nF C_(n)H_(2n+1) F H H nF.F C_(n)H_(2n+1) F F H nF.F.F C_(n)H_(2n+1) F F F nOF OC_(n)H_(2n+1) F H H nCl C_(n)H_(2n+1) Cl H H nCl.F C_(n)H_(2n+1) Cl F H nCl.F.F C_(n)H_(2n+1) Cl F F nCF₃ C_(n)H_(2n+1) CF₃ H H nCF₃.F C_(n)H_(2n+1) CF₃ F H nCF₃.F.F C_(n)H_(2n+1) CF₃ F F nOCF₃ C_(n)H_(2n+1) OCF₃ H H nOCF₃.F C_(n)H_(2n+1) OCF₃ F H nOCF₃.F.F C_(n)H_(2n+1) OCF₃ F F nOCF₂ C_(n)H_(2n+1) OCHF₂ H H nOCF₂.F C_(n)H_(2n+1) OCHF₂ F H nOCF₂.F.F C_(n)H_(2n+1) OCHF₂ F F nNS C_(n)H_(2n+1) NCS H H nS.F C_(n)H_(2n+1) NCS F H nS.F.F C_(n)H_(2n+1) NCS F F rVsN C_(r)H_(2r+1)—CH═CH—C_(s)H_(2s)— CN H H rEsN C_(r)H_(2r+1)—O—C_(s)H_(2s)— CN H H nAm C_(n)H_(2n+1) COOC_(m)H_(2m+1) H H

TABLE A

PCH

EPCH

BCH

CCP

EBCH

BECH

ECCP

CECP

CEPTP

CCH

D

PDX

ME

HP

EHP

FET

TABLE B

PTP-n[O]mFF

CPTP-n[O]mFF

CB15

C15

CGP-n-X (X = F, Cl, OCF₃ = _(“)OT”)

CGG-n.FX (X = F, Cl, OCF₃ = _(“)OT”)

CGU-n-X (X = F, Cl, OCF₃ = _(“)OT”)

GP-n-X (X = F, Cl, OCF₃ = _(“)OT”)

CDU-n-X (X = F, Cl, OCF₃ = _(“)OT”)

PGP-n-X (X = F, Cl, OCF₃ = _(“)OT”)

PGG-n-X (X = F, Cl, OCF₃ = _(“)OT”)

PGU-n-X (X = F, Cl, OCF₃ = _(“)OT”)

GGP-n-X (X = F, Cl, OCF₃ = _(“)OT”)

PGIGI-n-X (X = F, Cl, OCF₃ = _(“)OT”)

Inm

CBC-nm(F)

ECBC-nm

CCP-V2-m

CCP-nV2-m

CCP-V-m

CCP-nV-m

CCG-V-X (X = F, Cl, OCF₃ = _(“)OT”)

CCG-nV-X (X = F, Cl, OCF₃ = _(“)OT”)

CCP-V2-X (X = F, Cl, OCF₃ = _(“)OT”)

CC-m-V

CC-m-Vn

CCZU-n-X (X = F, Cl, OCF₃ = _(“)OT”)

CGZP-n-X (X = F, Cl, OCF₃ = _(“)OT”)

CCOC-n-m

The liquid crystal media according to the instant invention do contain preferably

-   -   seven or more, preferably eight or more compounds, preferably of         different formulae, selected from the group of compounds of         formulae of tables A and B and/or     -   one, two or more, preferably three or more compounds, preferably         of different formulae, selected from the group of compounds of         formulae of table A and/or     -   two, three, four or more, preferably five or more compounds,         preferably of different formulae, selected from the group of         compounds of formulae of table B.

EXAMPLES

The examples given in the following are illustrating the present invention without limiting it in any way.

However, they illustrate typical preferred embodiments. They show the use of typical and preferred constituents and illustrate their concentrations by way of example. Further they show possible variations of the physical properties of the compositions, illustrating to the expert which properties can be achieved and in which ranges they can be modified. Especially the combination of the various properties, which can be preferably achieved, is thus well defined for the expert.

Comparative Example 1

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 PCH-7F 9.0 T(N, I) = 70° C.  2 CCH-34 5.0 T(S, N) < −40° C.  3 CCH-35 4.0 n_(e) (20° C., 1.5606  4 PCH-301 13.0 589.3 nm) =  5 CCP-20CF3 5.0 Δn (20° C., 0.0760  6 CCP-30CF3 5.0 589.3 nm) =  7 CCP-40CF3 5.0 ε|| (20° C., 1 kHz) = 9.5  8 ECCP-3F 5.0 Δε (20° C., 6.1  9 BCH-3F.F 7.0 1 kHz) = 10 CCP-2F.F.F 10.0 γ₁ (20° C.) = 94 mPa · s 11 CCP-3F.F.F 13.0 k₁ (20° C.) = 10.5 pN 12 CCP-5F.F.F 6.0 k₃/k₁ (20° C.) = 1.25 pN 13 CCZU-2-F 6.0 V₀ (20° C.) = 1.40 V 14 CCZU-3-F 7.0 d · Δn = 0.55 μm Σ 100.0 V₁₀ (20° C.) = 1.66 V V₅₀ (20° C.) = 2.00 V V₉₀ (20° C.) = 2.43 V

This mixture does not contain any compounds of formulae I and II according to the present invention. It has an unfavourable combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to only moderate response times.

Example 1

A liquid crystal mixture according to the present invention is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCP-20CF3 4.0 T(N, I) = 74° C.  2 CCP-2F.F.F 7.0 T(S, N) < −40° C.  3 CDU-2-F 8.0 n_(e) (20° C., 1.5611  4 CDU-3-F 7.0 589.3 nm) =  5 CCZU-2-F 3.0 Δn (20° C., 0.0851  6 CCZU-3-F 15.0 589.3 nm) =  7 PGU-2-F 10.0 ε|| (20° C., 1 kHz) = 14.2  8 CGZP-2-OT 8.0 Δε (20° C., 10.0  9 CCG-V-F 3.0 1 kHz) = 10 CCP-V-1 3.0 γ₁ (20° C.) = 92 mPa · s 11 CC-5-V 12.0 d · Δn = 0.50 μm 12 CC-3-V1 12.0 V₁₀ (20° C.) = 1.31 V 13 CCH-35 3.0 14 CCH-3CF3 3.0 15 CCP- 4.0 20CF3.F Σ 100.0

This mixture has a very favourable value of Δn and an extremely good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to outstanding response times. It has even a slightly lower rotational viscosity compared to comparative example 1, though its clearing point is higher and its threshold voltage is lower.

Example 2

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCP-20CF3 4.0 T(N, I) = 82° C.  2 CCP-30CF3 3.0 T(S, N) < −40° C.  3 CCP-2F.F.F 10.0 n_(e) (20° C., 1.5546  4 CCP-3F.F.F 4.0 589.3 nm) =  5 CCZU-2-F 4.0 Δn (20° C., 0.0808  6 CCZU-3-F 13.0 589.3 nm) =  7 CGZP-2-OT 4.0 ε|| (20° C., 10.7  8 CC-5-V 16.0 1 kHz) =  9 CC-3-V1 11.0 Δε (20° C., 7.2 10 CCG-V-F 5.0 1 kHz) = 11 PGU-2-F 7.0 γ₁ (20° C.) = 91 mPa · s 12 CCH-3CF3 3.0 d · Δn = 0.50 μm 13 CCH-35 4.0 V₁₀ (20° C.) = 1.66 V 14 CCP- 4.0 20CF3.F 15 CCP- 4.0 30CF3.F 16 CCP- 2.0 50CF3.F 17 CCP-V-1 2.0 Σ 100.0

This mixture has a very favourable value of Δn and an extremely good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to outstanding response times. In particular it has a low rotational viscosity and an excellent phase range.

Example 3

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCP-20CF3 5.0 T(N, I) = 82.1° C.  2 CCP-30CF3 4.0 γ₁ (20° C.) = 93 mPa · s  3 CCP-2F.F.F 10.0 d · Δn = 0.50 μm  4 CCP-3F.F.F 4.0 V₁₀ (20° C.) = 1.62 V  5 CCZU-2-F 4.0  6 CCZU-3-F 10.0  7 CGZP-2-OT 7.5  8 CC-5-V 13.0  9 CC-3-V1 13.0 10 CCG-V-F 7.0 11 PGU-2-F 5.5 12 CCH-3CF3 5.0 13 CCH-35 2.0 14 CCP-20CF3.F 3.0 15 CCP-30CF3.F 3.0 16 CCP-50CF3.F 4.0 Σ 100.0

This mixture has a very favourable value of Δn and an extremely good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to outstanding response times.

Example 4

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound Conc./ No. Abbreviation % Physical Properties  1 CCP-20CF3 5.0 T(N, I) = 81° C.  2 CCP-30CF3 5.0 T(S, N) < −30° C.  3 CCP-2F.F.F 10.5 n_(e) (20° C., 1.5549  4 CCP-3F.F.F 5.0 589.3 nm) =  5 CCZU-2-F 4.0 Δn (20° C., 0.0800  6 CCZU-3-F 10.0 589.3 nm) =  7 CGZP-2-OT 5.0 ε|| (20° C., 1 kHz) = 10.2  8 CC-5-V 15.0 Δε (20° C., 6.8  9 CC-3-V1 15.0 1 kHz) = 10 CCH-35 3.0 γ₁ (20° C.) = 82 mPa · s 11 CCG-V-F 10.0 d · Δn = 0.50 μm 12 PGU-2-F 6.5 V₁₀ (20° C.) = 1.68 V 13 CCP-20CF3.F 3.0 14 CCH-3CF3 3.0 Σ 100.0

This mixture has a very favourable value of Δn and an extremely good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to outstanding response times.

Example 5

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound Conc./ No. Abbreviation % Physical Properties  1 CCP-2F.F.F 11.0 T(N, I) = 78° C.  2 CCZU-2-F 3.0 n_(e) (20° C., 1.5529  3 CCZU-3-F 13.0 589.3 nm) =  4 CCP-20CF3 5.5 Δn (20° C., 0.0779  5 CCP-30CF3 2.5 589.3 nm) =  6 CCP-20CF3.F 1.5 ε|| (20° C., 1 kHz) = 9.5  7 CC-3-V 14.0 Δε (20° C., 6.2  8 CC-3-V1 13.0 1 kHz) =  9 CC-5-V 12.0 γ₁ (20° C.) = 71 mPa · s 10 CCH-35 2.0 d · Δn = 0.50 μm 11 CGZP-2-OT 7.5 V₁₀ (20° C.) = 1.71 V 12 PGU-2-F 7.0 13 CCG-V-F 3.0 14 CCOC-3-3 1.5 15 CCP-V-1 1.5 16 CCH-3CF3 2.0 Σ 100.0

This mixture has a very favourable value of Δn and an extremely good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to outstanding response times. In particular it has an extremely low rotational viscosity.

Example 6

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound Conc./ No. Abbreviation % Physical Properties  1 CCH-35 1.5 T(N, I) = 70° C.  2 CCP-20CF3 6.0 n_(e) (20° C., 1.5637  3 CCP-30CF3 4.0 589.3 nm) =  4 CCP-20CF3.F 9.5 Δn (20° C., 0.0873  5 CCP-2F.F.F 11.5 589.3 nm) =  6 CGU-2-F 11.0 ε|| (20° C., 1 kHz) = 15.7  7 CCZU-2-F 4.0 Δε (20° C., 11.1  8 CCZU-3-F 15.0 1 kHz) =  9 CCZU-5-F 5.0 γ₁ (20° C.) = 124 mPa · s 10 PGU-2-F 8.0 d · Δn = 0.50 μm 11 CGZP-2-OT 10.0 V₁₀ (20° C.) = 1.11 V 12 CCH-3CF3 5.0 13 CC-3-V 7.0 16 CCOC-3-3 2.5 Σ 100.0

This mixture has a favourable value of Δn and a good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to good response times. It further has a high value of Δ∈ and is suited for operation with low voltage.

Example 7

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCH-35 4.0 T(N, I) = 71.5° C.  2 CCP-20CF3 6.0 T(S, N) < −30° C.  3 CCP-30CF3 7.0 n_(e) (20° C., 1.5606  4 CCP-40CF3 4.0 589.3 nm) =  5 CCP-2F.F.F 10.0 Δn (20° C., 0.0864  6 CCP-20CF3.F 5.5 589.3 nm) =  7 CGU-2-F 11.0 γ₁ (20° C.) = 131 mPa · s  8 CCZU-2-F 5.0 d · Δn = 0.50 μm  9 CCZU-3-F 15.0 V₁₀ (20° C.) = 1.17 V 10 CCZU-5-F 5.0 V₅₀ (20° C.) = 1.41 V 11 CC-5-V 3.0 V₉₀ (20° C.) = 1.78 V 12 PGU-2-F 6.5 13 CGZP-2-OT 10.0 14 CCH-3CF3 8.0 Σ 100.0

This mixture has a favourable value of Δn and a good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to good response times. It further has a high value of Δ∈ and is suited for operation with low voltage.

Example 8

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCH-35 5.0 T(N, I) = 70° C.  2 CCH-3CF3 8.0 T(S, N) < −40° C.  3 CCP-20CF3 8.0 n_(e) (20° C., 1.5602  4 CCP-30CF3 8.0 589.3 nm) =  5 CCP-2F.F.F 11.0 Δn (20° C., 0.0863  6 CCP-20CF3.F 7.0 589.3 nm) =  7 CGU-2-F 11.0 γ₁ (20° C.) = 133 mPa · s  8 CCZU-2-F 5.0 d · Δn = 0.50 μm  9 CCZU-3-F 15.0 V₁₀ (20° C.) = 1.13 V 10 CCZU-5-F 5.0 V₅₀ (20° C.) = 1.37 V 11 PGU-2-F 7.0 V₉₀ (20° C.) = 1.74 V 12 CGZP-2-OT 10.0 Σ 100.0

This mixture has a favourable value of Δn and a good combination of the clearing point-and rotational viscosity (T(N,I)/γ₁), which leads to good response times. It further has a high value of Δ∈ and is suited for operation with low voltage.

Example 9

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties  1 CCH-35 5.0 T(N, I) = 70° C.  2 CCH-3CF3 8.0 T(S, N) < −40 ° C.  3 CCP-20CF3 8.0 n_(e) (20° C., 1.5635  4 CCP-30CF3 8.0 589.3 nm) =  5 CCP-2F.F.F 10.0 Δn (20° C., 0.0885  6 CCP-20CF3.F 7.0 589.3 nm) =  7 CGU-2-F 11.0 γ₁ (20° C.) = 125 mPa · s  8 CCZU-2-F 5.0 d · Δn = 0.50 μm  9 CCZU-3-F 15.0 V₁₀ (20° C.) = 1.13 V 10 CCZU-5-F 5.0 V₅₀ (20° C.) = 1.37 V 11 PGU-2-F 8.0 V₉₀ (20° C.) = 1.73 V 12 CGZP-2-OT 10.0 Σ 100.0

This mixture has a favourable value of Δn and a good combination of the clearing point and rotational viscosity (T(N,I)/γ₁), which leads to good response times. It further has a high value of Δ∈ and is suited for operation with low voltage.

Example 10

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 CC-3-V 4.0 T(N, I) = 70.5° C. 2 CCH-3CF3 8.0 T(S, N) < −30° C. 3 CCP-20CF3 5.0 Δn (20° C., 0.0885 4 CCP-20CF3.F 12.0 589.3 nm) = 5 CCP-2F.F.F 11.0 γ₁ (20° C.) = 131 mPa · s 6 CGU-2-F 11.0 d · Δn = 0.50 μm 7 PGU-2-F 4.0 V₁₀ (20° C.) = 1.03 V 8 CCZU-2-F 5.0 9 CCZU-3-F 15.0 10  CCZU-5-F 5.0 11  CGZP-2-OT 11.0 12  CGZP-3-OT 9.0 Σ 100.0

This mixture has a favourable value of Δn and a good combination of the clearing point and rotational viscosity (T(N,I)/γ₁).

Example 11

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 CCP-2F.F.F 10.0 T(N, I) = 70.1° C. 2 CCP-20CF3 1.0 T(S, N) < −30° C. 3 CGZP-2-OT 15.0 Δn (20° C., 0.1021 4 CGZP-3-OT 11.0 589.3 nm) = 5 CCZU-2-F 5.0 γ₁ (20° C.) = 110 mPa · s 6 CCZU-3-F 15.0 d · Δn = 0.50 μm 7 CCZU-5-F 3.0 V₁₀ (20° C.) = 1.02 V 8 PGU-2-F 9.0 9 PGU-3-F 9.0 10  CC-3-V 15.0 11  CCH-3CF3 7.0 Σ 100.0

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2.

Comparative Example 2

A liquid crystal mixture is realised according to example E of WO 01/79379. This mixture has the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 CCP-2F.F.F 10.0 T(N, I) = 69.5° C. 2 CCP-20CF3 4.0 T(S, N) < 40° C. 3 CGZP-2-OT 14.0 Δn (20° C., 0.1052 4 CGZP-3-OT 10.0 589.3 nm) = 5 CCZU-2-F 4.0 γ₁ (20° C.) = 132 mPa · s 6 CCZU-3-F 15.0 d · Δn = 0.50 μm 7 CCZU-5-F 3.0 V₁₀ (20° C.) = 0.98 V 8 CGU-2-F 10.0 V₅₀ (20° C.) = 1.20 V 9 CGU-3-F 5.9 V₉₀ (20° C.) = 1.50 V 10  PGU-2-F 9.0 11  PGU-3-F 9.0 12  CC-3-V 11.0 Σ 100.0

This mixture, which is not using a compound of formula II according to the present application, has values for the clearing point, Δn and Δ∈ which are similar to those of example 11, but it has a significantly larger rotational viscosity.

Example 12

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 CCH-35 1.5 T(N, I) = 70° C. 2 CCP-20CF3 6.0 T(S, N) < −40° C. 3 CCP-30CF3 4.0 ε|| (20° C., 15.9 4 CCP-20CF3.F 9.5 1 kHz) = 5 CCP-2F.F.F 11.5 εΔ (20° C., 11.1 6 CGU-2-F 11.0 1 kHz) = 7 CCZU-2-F 4.0 n_(e) (20° C., 1.5642 8 CCZU-3-F 15.0 589.3 nm) = 9 CCZU-5-F 5.0 Δn (20° C., 0.0875 10  PGU-2-F 8.0 589.3 nm) = 11  CGZP-2-OT 10.0 γ₁ (20° C.) = 124 mPa · s 12  CCH-3CF3 5.0 d · Δn = 0.50 μm 13  CC-3-V 7.0 V₁₀ (20° C.) = 1.09 V 14  CCOC-3-3 2.5 V₅₀ (20° C.) = 1.33 V Σ 100.0 V₉₀ (20° C.) = 1.65 V

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2.

Example 13

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound Conc./ No. Abbreviation % Physical Properties 1 CCP-20CF3 5.0 T(N, I) = 75° C. 2 CCP-30CF3 5.0 n_(e) (20° C., 1.5538 3 CCP-2F.F.F 9.0 589.3 nm) = 4 CCP-3F.F.F 5.0 Δn (20° C., 0.0802 5 CCZU-2-F 3.0 589.3 nm) = 6 CCZU-3-F 12.0 ε|| (20° C., 1 kHz) = 10.7 7 CGZP-2-OT 7.0 εΔ (20° C., 1 kHz) = 7.2 8 CC-5-V 19.0 γ₁ (20° C.) = 79 mPa · s 9 CC-3-V1 9.0 d · Δn = 0.50 μm 10  CCG-V-F 8.0 V₁₀ (20° C.) = 1.45 V 11  PGU-2-F 8.0 V₅₀ (20° C.) = 1.82 V 12  CCH-3CF3 7.0 V₉₀ (20° C.) = 2.25 V 13  CCH-35 3.0 Σ 100.0

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2.

Example 14

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 PGU-2-F 8.0 T(N, I) = 70.5° C. 2 CGU-2-F 10.0 T(S, N) < −40° C. 3 CGZP-2-OT 11.0 n_(e) (20° C., 1.5669 4 CCP-2F.F.F 10.0 589.3 nm) = 5 CCZU-2-F 4.0 Δn (20° C., 0.0865 6 CCZU-3-F 9.0 589.3 nm) = 7 CCH-35 4.0 d · Δn = 0.50 μm 8 CC-5-V 18.0 V₁₀ (20° C.) = 1.46 V 9 CC-3-V1 10.0 V₅₀ (20° C.) = 1.75 V 10  CCH-3CF3 6.0 V₉₀ (20° C.) = 2.17 V 11  CCP-V-1 10.0 Σ 100.0

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2.

Example 15

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 PGU-2-F 9.0 T(N, I) = 70° C. 2 CGU-2-F 10.0 n_(e) (20° C., 1.5685 3 CGZP-2-OT 11.0 589.3 nm) = 4 CCP-2F.F.F 10.0 Δn (20° C., 0.0876 5 CCZU-2-F 4.0 589.3 nm) = 6 CCZU-3-F 9.0 γ₁ (20° C.) = 77 mPa · s 7 CCH-35 4.0 d · Δn = 0.50 μm 8 CC-5-V 18.0 V₁₀ (20° C.) = 1.44 V 9 CC-3-V1 9.0 V₅₀ (20° C.) = 1.72 V 10  CCH-3CF3 6.0 V₉₀ (20° C.) = 2.12 V 11  CCP-V-1 10.0 Σ 100.0

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2.

Example 16

A liquid crystal mixture is realised with the composition and properties given in the following table.

Composition Compound No. Abbreviation Conc./% Physical Properties 1 CC-5-V 20.0 T(N, I) = 69.5° C. 2 CC-3-V1 10.0 n_(e) (20° C., 1.5624 3 CCH-35 4.0 589.3 nm) = 4 PCH-53 5.5 Δn (20° C., 0.0872 5 CCH-3CF3 7.0 589.3 nm) = 6 CGU-2-F 3.5 d · Δn = 0.50 μm 7 PGU-2-F 8.0 V₁₀ (20° C.) = 1.50 V 8 PGU-3-F 1.5 V₅₀ (20° C.) = 1.79 V 9 CCZU-2-F 4.0 V₉₀ (20° C.) = 2.19 V 10  CCZU-3-F 14.0 11  CGZP-2-OT 11.0 12  CGZP-3-OT 8.0 13  CCP-30CF3 3.5 Σ 100.0

This mixture has a favourably high of Δn and a high value of Δ∈ and compares favourably with the mixture of the following comparative example, comparative example 2. 

1. A liquid crystal medium, comprising a dielectrically positive component A, which comprises one or more compounds of formula I

and one or more compounds of formula II

wherein R¹ and R² are, each independently, alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms, X¹ is F, Cl or fluorinated alkyl or fluorinated alkoxy, each with 1 to 4 C-atoms,

 independently of each other, are

Z¹¹ and Z¹² are each a single bond, L¹¹ is F, L¹² is H or F,

Z² is —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O— or a single bond, and X² is F, Cl or fluorinated alkyl or fluorinated alkoxy each with 1 to 4 C-atoms, wherein a compound of formula II-1d is present in the medium

wherein R² is as defined above, and at a concentration of 29.5% or more of one or more compounds of formula III

wherein R³ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms,

 is

Z³¹ and Z³² are, independently of each other, —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂, —CH₂—O—, —O—OH₂—, —CO—O— or a single bond, and L³¹ and L³² are, independently of each other, H or F.
 2. A liquid crystal medium according to claim 1, wherein component A further comprises one or more compounds of formula IV

wherein R⁴ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms,

 is

Z⁴¹ and Z⁴² are, independently of each other, —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O— or a single bond, and L⁴¹ and L⁴² are, independently of each other, H or F.
 3. A liquid crystal medium according to claim 1, further comprising a dielectrically neutral component B, which comprises one or more compounds of formula V

wherein R⁵¹ and R⁵², independently of each other, are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms, Z⁵ is —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O—, —CH═CH—, CF═CF—, —CF═CH—, —CH═CF— or a single bond, and n is 0 or
 1. 4. A liquid crystal medium according to claim 1, further comprising a dielectrically negative component C.
 5. A liquid crystal medium according to claim 1, wherein one or more compounds of formula I are of formulae I-1 to I-3

wherein R¹, L¹¹ and L¹² have the meanings given in claim 1, and L¹³ is H or F.
 6. A liquid crystal medium according to claim 1, wherein one or more compounds of formula II are of formulae II-1 and II-2

wherein R², X² and

 have the meanings given in claim
 1. 7. A liquid crystal display comprising a liquid crystal medium according to claim
 1. 8. A liquid crystal display according to claim 7, which is addressed by an active matrix.
 9. A liquid crystal medium according to claim 2, further comprising a dielectrically neutral component B, which comprises one or more compounds of formula V

wherein R⁵¹ and R⁵², independently of each other, are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms, Z⁵ is —CH₂—CH₂—, —CF₂—CF₂—, —CF₂—O—, —O—CF₂—, —CH₂—O—, —O—CH₂—, —CO—O—, —CH═CH—, CF═CF—, —CF═CH—, —CH═CF— or a single bond, and n is 0 or
 1. 10. A liquid crystal medium according to claim 2, wherein one or more compounds of formula I are of formulae I-1 to I-3

wherein R¹, L¹¹ and L¹² have the meanings given in claim 2, and L¹³ is H or F.
 11. A liquid crystal medium according to claim 2, wherein one or more compounds of formula II are of formulae II-1 and II-2

wherein R², X² and

 have the meanings given in claim
 2. 12. A liquid crystal medium according to claim 3, wherein one or more compounds of formula I are of formulae I-1 to I-3

wherein R¹, L¹¹ and L¹² have the meanings given in claim 3, and L¹³ is H or F.
 13. A liquid crystal medium according to claim 3, wherein one or more compounds of formula II are of formulae II-1 and II-2

wherein R², X² and

 have the meanings given in claim
 3. 14. A liquid crystal medium according to claim 5, wherein L¹³ is F.
 15. A liquid crystal medium according to claim 1, comprising a compound of formula I-1

wherein R¹ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms, L¹¹ and L¹³ is F, and L¹² is H or F.
 16. A liquid crystal medium according to claim 15, comprising a compound of formula I-1d

wherein R¹ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C-atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C-atoms.
 17. A liquid crystal medium according to claim 1, wherein the one or more compounds of formula III are present at a concentration of 29.5%–45%.
 18. A liquid crystal medium according to claim 1, wherein the one or more compounds of formula III are present at a concentration of 33%–45%.
 19. A liquid crystal medium according to claim 1, wherein the one or more compounds of formula III are present at a concentration of 33–37%. 